Speaker
Description
The modification in jets measured in heavy-ion collisions as compared to jets measured in pp collisions is a rich source of information on the medium properties. The medium-induced modifications are typically seen more clearly at low-$p_{\rm T}$, where full jet reconstruction is difficult due to the very large background in heavy ion collisions. Two-particle correlations provide a way to study jets in the low- and intermediate-$p_{\rm T}$ regime. Jet fragmentation is observed as a peak around $(\Delta\eta, \Delta\phi)=(0,0)$ in two-particle correlations, where $\Delta\eta$ and $\Delta\phi$ are the differences in pseudorapidity and azimuthal angle, respectively, between a trigger particle and associated particles.
In this talk, we will present ALICE measurements of $I_{\rm AA}$, the jet peak yield in Pb-Pb divided by the yield from pp collisions, at $\sqrt{s_{\rm NN}} = 2.76$ TeV. From $\Delta\eta$-dependent $I_{\rm AA}$, we observe that jets with 6$<$$p_{\rm T,trig.}$$<$8 GeV/c and 8$<$$p_{\rm T,trig.}$$<$15 GeV/c show a narrowing in pseudorapidity. This effect is prominent in central collisions and for high trigger momentum while it vanishes in peripheral collisions or for low trigger momentum. From the integrated, $p_{\rm T}$-dependent $I_{\rm AA}$ we see enhancement at low-$p_{\rm T}$ in central collisions. These observations can be used to constrain energy loss models, particularly models that predict broadening of the jet by interactions with the medium.
List of tracks | Charge fluctuations, correlations and balance functions |
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